How to Make Cement Foundation

Cement--rough look, strong finish.

While its rough texture is not ideal for patios or other surfaces where bare feet may walk, because of its durability, cement makes a good foundation for many types of structures. The most common projects of this type for self-builders are storage buildings and sheds. Learning how to pour a square foundation for your new building yourself can save you a lot of money, especially since you can then purchase a modular style rather than hiring a contractor to construct the structure on-site.

Things You'll Need

• Cement
• 2 boards, 2-by-4, as long as your finished foundation should be
• 2 boards, 2-by-4, each 2 feet longer than your finished foundation should be
• Clamps
• Tape measure
• 12 carpentry nails
• Hammer
• Pencil (optional)
• 2-by-2-inch wooden pegs, approximately 10-inches-long
• Hacksaw
• Shovel
• Garden hose with fine mist attachment
• Long-handled tamp
• Protective clothing
• Safety goggles
• Gloves
• Wheelbarrow
• Reinforcing rod, 1 foot shorter than the width of your foundation
• Piece of No. 3 rebar, as long as the perimeter of your foundation plus 6 feet
• Tie wires
• Metal screed
• Rubber float

Instructions

1. Decide how large your foundation needs to be. Multiply the length and width (in feet) to calculate the surface area, then multiply this number by .33, to make the foundation a standard 4 inches thick.

2. Go to a home improvement or hardware store and research the types of cement available. Some cements now come in colors that may work better with your décor than the standard gray. Choose a cement and read the packaging to find out how much area it will cover, since the side of each product may vary. Compare these measurements with your calculated ones. Buy enough cement to complete your foundation. Ask the store to mix the cement on-site.

3. Gather the lumber, nails, hammer, a pencil and a tape measure in the general area where your foundation will be poured. Measure each longer board from either end, and use the pencil to mark 1 foot in from each end. Line up the end of a shorter board so that the long edge spans the width of the longer board at the 1 foot mark. You may wish to secure the boards together with a clamp. Use a hammer to sink a line of three evenly spaced nails through the longer board into the edge of the shorter board. Attach the other shorter board to this long board in the same way. Butt the remaining longer board up against the loose ends of the short boards and adjust it so that the ends are aligned with the 1 foot marks on the long board. Clamp the board into place, then hammer it to the shorter boards. With a tape measure, measure the inside of the frame to double-check that all of the sides are even.

4. Gently move the frame into place, if it is a bit off. Place a 2-by-2-inch wooden pin every 2 feet around the entire frame by pressing them gently into the soil. Use a hammer to secure the pins about halfway into the ground. These pins will keep the frame from shifting as the cement cures. Cut the top off of each peg with a hacksaw so that it is even with the top of the wooden frame.

5. Make a trench with your shovel around the inside edge of your foundation frame. It should be 4-inches-deep and approximately as wide as the spade of your shovel. The edges of the foundation will be thicker, making the foundation itself stronger.

6. Spray the soil in the frame with a garden hose until it is evenly moistened. Tamp the soil to make it level and flat with a long-handled tamp

7. Put on long sleeves, long pants and cover your feet completely. Put on safety goggles and cover your hands with gloves. The cement may splash a little during pouring, and wet cement can stick to and damage skin.

8. Transfer your cement into a wheelbarrow and push it to the edge of the frame so that the end hangs over the frame (see Resources for information about how to make cement yourself). Pour enough cement from the wheelbarrow into the frame to make a level, 1-inch layer. Smooth and spread the cement with your shovel or have someone else do it as you pour.

9. Place the reinforcing rod approximately in the center of the wet cement. Keep the rod as straight as possible while you position it. Approximately 2 inches from the edges of the frame, lay the rebar around the perimeter. Carefully bend it to fit around each corner. Secure the reinforcing rod to the rebar with tie wire where they overlap, and also use tie wire to fasten together the overlapping ends of the rebar.

10. Empty the remainder of the cement into the frame until it is nearly full. Use a hammer to tap each side of the frame exterior two or three times to settle the cement.

11. Move a metal screed back and forth in a sawing motion as you drag it from one side of the frame to the other to smooth and level the cement. Choose a lighter screed so that you do not create a depression in the cement.

12. Using large, arching movements, go over the surface of the cement with a rubber float until it is smooth. Cure the cement for about 30 minutes so that it can settle. Float the surface of the foundation again. Wait another 30 minutes. Use the float to smooth the surface again and allow the cement to rest until the top layer is no longer wet.

13. When all of the surface moisture has evaporated, smooth the surface of the cement with the float for the last time. Cure the cement for at least three days, longer if your foundation is particularly large. During this time, evenly and lightly spray the slab once a day with your garden hose with the fine mister attachment.

14. Lift the frame directly off of the slab foundation with help after it has finished curing. Remove the nails and take the frame apart to reveal your new foundation, if the frame does not lift easily.

References

• BuildEazy: How to Make a Concrete Slab

Resources

• BuildEazy: How to Mix Concrete